Power supply device and image forming apparatus implementing ripple voltage suppression

Abstract

A power supply device that applies a voltage in which a direct-current (DC) voltage and an alternating-current (AC) voltage are superimposed on each other to a charging member that charges an image bearer, includes: an AC voltage generation circuit that generates the AC voltage; a DC voltage generation circuit that generates the DC voltage; a DC current detection circuit provided on an output terminal side of the DC voltage generation circuit, which detects an output DC current flowing into the image bearer; and a reduction circuit that reduces an inflow of an AC current to the DC current detection circuit.

The invention claimed is: 
     
       1. A power supply device that applies a voltage in which a DC voltage and an AC voltage are superimposed on each other to a charging member that charges an image bearer, comprising:
 an AC voltage generation circuit that generates the AC voltage; 
 a DC voltage generation circuit that generates the DC voltage; 
 a DC current detection circuit provided on an output terminal side of the DC voltage generation circuit and that detects an output DC current flowing into the image bearer; and 
 a reverse waveform applicator circuit that applies a reverse phase waveform of a ripple voltage expected in the DC current detection circuit to the DC current detection circuit. 
 
     
     
       2. The power supply device according to  claim 1 ,
 wherein the DC current detection circuit includes:
 a detection analog-to-digital (AD) converter circuit that detects the output DC current flowing into the image bearer; and 
 a current detection element including a resistor of the detection AD converter circuit, and 
 
 wherein the reverse waveform applicator circuit applies the reverse phase waveform of the ripple voltage to a DC current detection line between the detection AD converter circuit and the current detection element. 
 
     
     
       3. The power supply device according to  claim 2 ,
 wherein the reverse waveform applicator circuit is configured to output a control signal for causing the AC voltage generation circuit to generate a designated AC voltage, and 
 wherein the reverse waveform applicator circuit includes:
 a ripple-voltage memory that stores in advance a ripple waveform to be generated per designated AC voltage of the control signal; 
 processing circuitry configured to expect a ripple waveform to be generated based on an ongoing control signal and calculate a reverse waveform of the expected ripple waveform; and 
 a digital-to-analog (DA) converter circuit that generates the calculated reverse waveform of the ripple waveform and outputs the generated reverse waveform to the DC current detection line. 
 
 
     
     
       4. The power supply device according to  claim 3 , further comprising:
 a phase detector circuit that detects a phase of a ripple voltage of the output DC current in the DC current detection line, 
 wherein the reverse waveform applicator circuit outputs the calculated reverse waveform of the ripple waveform to a position located downstream of a position at which the phase detector circuit is connected of the DC current detection line in accordance with the detected phase of the ripple voltage. 
 
     
     
       5. The power supply device according to  claim 4 ,
 wherein the reverse waveform applicator circuit further includes:
 a deviation-amount memory that stores in advance a relationship of a deviation amount of an actual detection value of a detection value at a measurement point for a generated ripple voltage per designated AC frequency, and 
 
 wherein the processing circuitry is configured to expect a ripple waveform regarding a deviation amount based on the control signal and the stored deviation amount at the measurement point and calculate a reverse waveform of the expected ripple waveform regarding the deviation amount. 
 
     
     
       6. A power supply device that applies a voltage in which a DC voltage and an AC voltage are superimposed on each other to a charging member that charges an image bearer, comprising:
 an AC voltage generation circuit that generates the AC voltage; 
 a DC voltage generation circuit that generates the DC voltage; and 
 a control device connected to an output terminal side of the DC voltage generation circuit and configured to output a control signal for causing the AC voltage generation circuit to generate a designated AC voltage and calculate an output DC current flowing into the image bearer, 
 wherein the control device includes:
 an AD converter circuit connected to the output terminal side of the DC voltage generation circuit and that detects a DC current; 
 a ripple-voltage memory that stores in advance a ripple waveform to be generated per designated AC voltage of the control signal; and 
 processing circuitry configured to expect a ripple waveform to be generated based on an ongoing control signal, calculate a reverse waveform of the expected ripple waveform, and set a value obtained by adding the calculated reverse waveform to a DC current including a detected ripple as the output DC current. 
 
 
     
     
       7. An image forming apparatus comprising:
 the power supply device according to  claim 1 ; 
 the image bearer; 
 the charging member configured to charge the image bearer; and 
 a control device configured to calculate a surface potential of the image bearer based on the output DC current. 
 
     
     
       8. An image forming apparatus comprising:
 the power supply device according to  claim 6 ; 
 the image bearer; and 
 the charging member configured to charge the image bearer; 
 the control device further configured to calculate a surface potential of the image bearer based on the output DC current.